Well, being a Grand National owner, I'm going to have to say the Buick GNX. Few people have heard of either car, unless you're a real car buff, and that's one of the reasons I love it.
I absolutely love the history behind the car -- it's proof of what happens when engineers are turned loose. The fact that Buick underrated its power so that it wouldn't outshine the Corvette makes me chuckle. Here's the cheesy, but mostly accurate Car and Driver segment on the GNX:
http://www.youtube.com/watch?v=1G6wtnmdZhE